Please seek guidance from those experienced in this field: regarding the issue of concrete strength
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I want to build a recycling pool that is 4 meters long and 3 meters wide, with a underground section that is 2.5 meters deep. I am considering using reinforced concrete or brick construction. It will be located by the Yangtze River, where the soil is sandy. I plan to construct walls that are 120 mm thick; I’m not sure if such thickness of concrete will provide sufficient strength How thick should the bricks be if built with bricks? I’m not in this field, so there are many things I don’t understand. Now I have to take charge of them as well – it’s overwhelming! I would appreciate your guidance on the things to pay attention to during construction, including specific advice regarding the type of rebar to use, the density of the rebar network, and the ratio of cement to aggregate Wait! Not grateful at all! Last edited by Welcome on 2009-3-6 12:47]
I’m not sure how it works, so let’s take the case of a structure without a roof as an example.
I. First, regardless of whether to use bricks or concrete, it’s necessary to carry out internal force calculations first.
1. For sandy soil located near a water source, the earth pressure should be calculated using the principle of separating soil and water effects; I won’t go into details here – just search on Baidu and you’ll find what you need.
2. For sandy soil in a saturated state, its unit weight is 9 kN/m³. The earth pressure coefficient should be calculated based on “static earth pressure,” and a value of 0.5 can be used. Assume the groundwater level is at ground level. Earth pressure is considered a permanent load, with a partial coefficient of 1.35.
3. The live load on the surface is 5 kN/m²; this value also needs to be multiplied by the static earth pressure coefficient of 0.5, resulting in a partial coefficient of 1.0.
4. Find a handbook on static calculations for building structures.
a. For earth pressure, treat it as a triangular load with three fixed edges and one free edge; this will allow you to directly determine the design value of the beam bending moment.
b. For water pressure, also treat it as a triangular load with three fixed edges and one free edge; this will give you the design value of the beam bending moment.
c. For live loads, treat them as rectangular loads with three fixed edges and one free edge; this will help you determine the design value of the beam bending moment.
d. The design value of the beam bending moment is obtained by adding up these three types of moments.
II. Using bricks is certainly simpler and more cost-effective, so it should be given priority.
1. Refer to the “Code for Design of Masonry Structures” GB 50003-2001 – please read it carefully.
2. Based on the calculated design values for bending moments, it’s clear that 240-mm thick walls are not sufficient; use 370-mm thick walls instead.
III. If concrete is used, refer to the “Code for Design of Concrete Structures” GB 50010-2002.
1. Based on the calculated design values for bending moments, 200-mm thick concrete may not be enough; in that case, use 250-mm thick concrete.
2. Determine the required reinforcement strength based on the initial thickness of the concrete slab; I won’t go into details here – use existing software for this purpose.
3. Use grade 2 steel bars with diameters of 12 or 14 mm, along with 8-mm diameter distribution bars.
4. Use a partial coefficient of 1.0 for both permanent and live loads, then recalculate the internal forces to obtain the standard values for bending moments. Use these values to check for cracks.
IV. Reinforcement for the bottom slab (if bricks are used as a base, there’s nothing much to consider).
1. Calculate the buoyant force acting on the bottom slab, and subtract the weight of the slab itself; use a partial coefficient of 1.35.
2. As before, consult the handbook to calculate the internal forces, and then determine the required reinforcement based on those forces and the slab thickness.
V. Check for uplift resistance (I doubt it’s possible to meet the requirements in this case).
1. In the worst-case scenario, there’s no water in the pool, and the groundwater level is at ground level.
2. The weight of the pool itself must be greater than or equal to the buoyant force.
VI. It’s unclear whether waterproofing is necessary; refer to the “Code for Design of Reinforced Concrete Pools” for guidance.
I can’t go any further into detail – I’m almost ready to help you with the calculations
I. First, regardless of whether to use bricks or concrete, it’s necessary to carry out internal force calculations first.
1. For sandy soil located near a water source, the earth pressure should be calculated using the principle of separating soil and water effects; I won’t go into details here – just search on Baidu and you’ll find what you need.
2. For sandy soil in a saturated state, its unit weight is 9 kN/m³. The earth pressure coefficient should be calculated based on “static earth pressure,” and a value of 0.5 can be used. Assume the groundwater level is at ground level. Earth pressure is considered a permanent load, with a partial coefficient of 1.35.
3. The live load on the surface is 5 kN/m²; this value also needs to be multiplied by the static earth pressure coefficient of 0.5, resulting in a partial coefficient of 1.0.
4. Find a handbook on static calculations for building structures.
a. For earth pressure, treat it as a triangular load with three fixed edges and one free edge; this will allow you to directly determine the design value of the beam bending moment.
b. For water pressure, also treat it as a triangular load with three fixed edges and one free edge; this will give you the design value of the beam bending moment.
c. For live loads, treat them as rectangular loads with three fixed edges and one free edge; this will help you determine the design value of the beam bending moment.
d. The design value of the beam bending moment is obtained by adding up these three types of moments.
II. Using bricks is certainly simpler and more cost-effective, so it should be given priority.
1. Refer to the “Code for Design of Masonry Structures” GB 50003-2001 – please read it carefully.
2. Based on the calculated design values for bending moments, it’s clear that 240-mm thick walls are not sufficient; use 370-mm thick walls instead.
III. If concrete is used, refer to the “Code for Design of Concrete Structures” GB 50010-2002.
1. Based on the calculated design values for bending moments, 200-mm thick concrete may not be enough; in that case, use 250-mm thick concrete.
2. Determine the required reinforcement strength based on the initial thickness of the concrete slab; I won’t go into details here – use existing software for this purpose.
3. Use grade 2 steel bars with diameters of 12 or 14 mm, along with 8-mm diameter distribution bars.
4. Use a partial coefficient of 1.0 for both permanent and live loads, then recalculate the internal forces to obtain the standard values for bending moments. Use these values to check for cracks.
IV. Reinforcement for the bottom slab (if bricks are used as a base, there’s nothing much to consider).
1. Calculate the buoyant force acting on the bottom slab, and subtract the weight of the slab itself; use a partial coefficient of 1.35.
2. As before, consult the handbook to calculate the internal forces, and then determine the required reinforcement based on those forces and the slab thickness.
V. Check for uplift resistance (I doubt it’s possible to meet the requirements in this case).
1. In the worst-case scenario, there’s no water in the pool, and the groundwater level is at ground level.
2. The weight of the pool itself must be greater than or equal to the buoyant force.
VI. It’s unclear whether waterproofing is necessary; refer to the “Code for Design of Reinforced Concrete Pools” for guidance.
I can’t go any further into detail – I’m almost ready to help you with the calculations
Thank you so much! But I still can’t understand it! Could you help me calculate how thick the concrete needs to be?